A man who unsuccessfully claimed at trial that his rape victim agreed to have sex with him after seeing “all of his manhood” hanged himself at Rikers Island just hours after a judge sentenced him to 20 years behind bars.

Kevin Mitchell, 22, had claimed at trial that the woman – a stranger – went with him willingly after seeing how happy he was to see her in December 2001, authorities said.

“He says she saw his erection,” said one law-enforcement source. “That she decided to go with him because she saw all of his manhood.”

A jury didn’t buy it after hearing from other witnesses who testified they saw Mitchell drag the 19-year-old victim off Flatbush Avenue and into an apartment, authorities said.

“He’s punching her and she’s screaming with him all the way,” the source said.

Brooklyn Supreme Court Justice Albert Tomei sentenced Mitchell to 20 years Monday. Mitchell was found hanging from a bed sheet in his cell at around 2:20 a.m. Tuesday, officials said.